sleipner vector fins or seakeeper 16 for a 75 ft ?

Portofino said:
Pascal please can you confirm that on the recent test the Sunseeker guys did not report any technical problems that may have accounted for in your view the unsatisfactory motion of the boat at rest with the Sleipner fins ?

The 2x sk9 sounds a good idea .

I suspect if sleipner fins and 1sk9 there’s no need to run both together .
It’s one the fins when motoring along with dynamic stability that’s more than enough.

And the gyro at anchor as the fins we assume were not good enough in this particular application.
Problem is a sk 9 on its own big enough on its own , with not much if any assistance from the fins ?

A pair of sk9 ,s sounds the best idea in this boat ,based on the fins did not seem to do a lot at rest with this boat .
Click to expand...
Porto, you're making a lot of statements and (in your words) assumptions about this. You have never owned or run any boat with either gyros or fins. The most you've done is maybe have a short ride in one. In contrast there are people on here with many years of both gyro and fin ownership as well as hands on installation and set up experience. That includes far more experience than any s/seeker salesman. Just saying
 
hi Jfm,

we noticed some difference but this was not huge, at least not comparable to my current system. the sunseeker salesman had to look on the screen if the system was on or off modus. that's what I told them immediatly on my seakeeper system sure you know that the system is in on or off modus, you don't need to see on the screen. my friend was also on board this sea trial and saw on the screen that the fins were moving but was also not impressed by the zero speed performance. he has a predator 62 with no stablization system, only experience onboard my pred 60 with the seakeeper. So your opinion is that the sleipner fins and a smaller gyro can good work together in case they are not running on the same computer. my opinion is that if this systems are both installed they both have their own computer I suppose. what I also noticed was that everything looks a little bit unnatural even underway. 7-8 years ago I ordered a new pred 60 with IPS engines. Sunseeker adviced me this engines because of more speed, less consumption. I sold this boat after 3 months, for me it was nothing comparing to shaft drive and I part exchange this boat again which costed me a lot of money and bought a new stock boat with Man's (current boat) Probably a lot of people are quit happy with IPS but for me the driving experience was horrible. that' why I want to be very careful with this decision. It would be a pitty when this fins would not be working as they should do, then it is a missed chance. I think I just wait what the factory is all proposing to me and then I have to decide fins- gyro or gyro-gyro...
 
It's entirely your choice pascal and you must buy the boat you like best

But to say fins feel unnatural underway to the point where you might not like the boat, is amazing. You might be the only guy on the planet to think that!

As for only a slight difference in "at anchor" mode, I'm sticking to my guns and saying something was wrong. I and my brother have had 4 sets of STAR fins between us and for sure they all show a big difference between on/off at anchor. Fit a seakeeper though if you think the cost makes sense (cost in terms of space burn and weight, not money).
 
jfm said:
Porto, you're making a lot of statements and (in your words) assumptions about this. You have never owned or run any boat with either gyros or fins. The most you've done is maybe have a short ride in one. In contrast there are people on here with many years of both gyro and fin ownership as well as hands on installation and set up experience. That includes far more experience than any s/seeker salesman. Just saying
Click to expand...

Let’s try and stick to playing the ball not the man :)

I don,t think re reading Pascals post of test drive of the system and further probing Q from pascal who’s kindly answered , I did much assuming.

It’s other assuming the system is bust , not Me .

If you re read one of my posts above about the guy who has the Pershing 115 .
I did not want to say anything then trying to be diplomatic ( think MapishM may be right about salesmen btw ) but now pascals mentioned an earlier Sunseeker disappointing sale becoming a victim to the IPS rhetoric , my friend had two sleipner curved fin Preditors ( the larger out of 4 ) - felt he was a victim of sales rhetoric too .Wife was disappointed and did not want to go out on it - partly due to sea sickness .
It too was an expensive error buying the Pred 115 .It was sold after a season and switch ( berth size similar) to a gyro ed Pershing same L
Completely different - better ride , running and anchor .Wife happy with it .

That’s why all along I,ve said talk to the captains or take a test drive .

There’s no point entering a debate here on the whys and where’s , as said there’s a grey area with planing hulls .

It either works to the customers satisfaction
Or it does not , it falls short

Let’s think positive, at least there’s another system SK gyros for the Sunseeker which , others like Riva , Pershing use , to the satisfaction of the customers.

There no point saying in a king Canute way sleipner fins should work cos on paper I see no reason why not .

In reality they are not satisfactory- so let’s all move on ps


Pascal clutching at straws, you could if there’s a boat for demo in the SoF and try again on another S fined boat .
Just to be sure if they are satisfactory at rest and running .

What did you mean by
“ I also noticed everything looks a little bit unnatural EVEN underway “ ?

I suppose like Mrs Pred 115 Wife does it have to feel right or natural ?

Happy to hear if possible what “unnatural “. In your shoes means .
 
Last edited:
portofino,

unnatural is difficult to explain, it was a little bit like my autopilot was on but it wasn't. is it the feeling of the fins sweeping in the water when you drive I don't know... no experience with fins except this one time. below is the comment from the factory, for them was everything ok. For me everything look strangs too, almost everyone is happy with the fins and I have much doubt this system.
(Regarding the stabiliser fins on the 74 predator that you sea trialled last Thursday. Meanwhile I have got an answer from the factory the fins were working fine and were fully operational for them. they gone send data from the sleipner engineer.
 
jfm said:
It's entirely your choice pascal and you must buy the boat you like best

But to say fins feel unnatural underway to the point where you might not like the boat, is amazing. You might be the only guy on the planet to think that!

As for only a slight difference in "at anchor" mode, I'm sticking to my guns and saying something was wrong. I and my brother have had 4 sets of STAR fins between us and for sure they all show a big difference between on/off at anchor. Fit a seakeeper though if you think the cost makes sense (cost in terms of space burn and weight, not money).
Click to expand...
That 4
Let’s drill down through that data .
It sounds like 4 happy boats .It is .
But your Bros two are not good comparison and should be taken out of the sample .
This is because one was a displacement boat and the other a semi displacement which is used mainly in D mode .
The hull shape s are not hard chine pure planing boats .

So now there were two :)

Yours is the same hull - 2x sq 78 ,s so in effect you are double counting for the purpose of throwing numbers about .
So now we are down to —-

ONE - yours which I outlined earlier on , using 4 is misleading.

That ONE hull counts as it’s a hard chine planing hull and similar size ., to the Pred Sport Y 74 .
I would if we are grouping hull types put yours it in the same group as Pascals


There’s obviously some subtle difference s between the Sq 78 and sport Y 74 , but as said no point wasting neurones working out why .

Pascal
Data —from manufacturers - be careful- sliding pieces of paper across a table that say this that and the other , X. Y Z reduction in roll etc does not change what it feels like .

I,ve been looking at studying fin stabilisation trying to find studies NOT from the manufacturers, ie unbiased .
There aren,t many .Plenty of sales rhetoric as you would expect but you have to cut through that .
In this one there’s an interesting piece that says the “ crew did not notice “ even though there was recordings of significant changes on paper .
It’s linked to dynamic stability inherent in Planing hulls —- you know they ( some more than others ) firm up going faster

http://www.dtic.mil/dtic/tr/fulltext/u2/a062561.pdf

Seasickness
It’s a disorientation of the brain , from what it see to what it’s feels .
If what it’s been told by the eyes visually something that does not match what it’s been told by movement sensors in the ear , then it thinks the body has been poisoned so tells the stomach to empty - just in case .

So a scientist armed with sheets of data can show you X % reduction in this that an the other , claiming the ride is better .
That not what your brain ( via eyes n ears ) is getting —- it feels “ unnatural “

So we have to split the maths out - it’s correct not doubting that never have —- then add in the customer the biological bit ,the difficult part

Hence test each time .

Hope that makes sense .
 
@porto, "assume" was your word not mine. As I said.
It's hard to make time to deal with all your "tech" points so am mostly happy to agree to disagree.
@pascal, if the fins were working properly but the boat still rolled, then either the waves were big or they hit the boat's natural roll period. There is not that material a difference between the anti roll torque x time of 2 x 1msq fins and sk9. I suggest the boat would have rolled similarly with working fins vs working sk9

As discussed I still don't buy the "unnatural feel underway" but that is just personal preference. One thing absolutely not in any debate/dispute is that fins completely eliminate roll underway in a big sea whereas gyros can't and don't. In op you said that was important.

Bottom line is that the best spec imo is fin+gyro together and that will be my next boat. Ideally with integrated software, but no-one is selling that yet.
 
Adding the biological element , the customer is the most important thing .
It’s easy to get carried away with the science / engineering / maths , to the point the customer is being dictated to .
In the sense —— told by experts ( that inc you JFM btw ) this is what you want .

So in my view to way to unlock this , cross the technobabble spewed out by group engineers / expert s and connect with - customer s is this ——-
Needs a double blind study .
A range of boats three of each .
One no stabs , second sleipner fins , third SK gyros and maybe a 4 th both , or a 5 th another brand of fin .
Then in the same sea state s , various over how many days take out a group of random chosen humans a typical x section of the target demograph s ( not 5 year olds ) all fit n healthy no medical complications.##

Because it’s blind neither the helm * or the subjects know which boat they are ridding in .

Leave port with what ever system On
Ask them the subjects to score the ride in a scale of feeling “ unnatural “ to nauseating, etc some sort of score .

* fit the comtols fit the stabs away from the helm sight - genys and anything else on and identical.

Helm runs round the same series of boys with an interesting seaction eg for JFM cap d Antibes :)
Record all data roll etc with the same equipment identically .

Then repeat how ever many times with how ever many folks in how ever many sea different sea states to get so meaningful comparison data of “ feelings “

Then x match the stabs system using the none stabs one as a control
To the data printed AND to the “ feelings “

You probably find either they ( stabbed ) all score the same or something interesting? In the feeling
And asJFM infers the paper data will score the sleipner s the highest , but that’s not the point .

What we are looking for is which one the crowd hate the most ——- we don,t know that for sure .

The point is which feels the most natural, which do the crowd prefer- if any and how far ( assuming again ) does the none stabilised boat lag behind in the human scoring ?
We know it will be bottom in the paper results.

Remember niether helm or people know which boat is which it’s double blind .
Can be done @ D and P speeds .

##
The sample can be grouped in sex and age bands 20-30 , 30 - 40 etc up to what ever .
You could do other stuff as well like wear glasses or even height and sitting or standing .looking Fwds looking backwards.
Build a spread sheet

We I need min three typical market boats and about 500 volunteers and 30 helms ( 3x10 ) new set every day and 10 days of crap weather .
 
Last edited:
pascalsunseeker said:
we noticed some difference but this was not huge, at least not comparable to my current system.
Click to expand...
Hang on, this is different from "we pushed the fins on and off and even the sunseeker people couldn't say it the system was off or on".
Which was the reason why I said that the system HAD to be malfunctioning. By definition, so to speak.
If the stabs did make some difference, but not as much as you expected/wanted, then it's a different matter altogether.

One question about your test: when the fins were turned on and off, did they give the system a bit of time to stabilize the vessel, after turning the system on/off?
I am asking because an inherent characteristic of gyros is that their effect is more immediate (after the initial flywheel spool-up, obviously), while fins are more dependent on predictive algorithms and they need a bit of time to reach their full effectiveness.
I'm only talking of zero speed, mind: under way fins are immediately effective.
The short delay at zero speed is not an issue in real world usage, anyway: there's no reason to play with the system turning it on and off at short intervals just for sake of testing them - as they might have done during your seatrial.

You can get an idea of the initial reaction time of fins at zero speed in the video I posted previously, made during the stabs commissioning/tuning.
The video starts right after the fins were center locked, hence making the boat behave as if she would have no stabs at all (actually there is a bit of resistance to roll also with the fins locked, compared to no fins at all, but this is negligible).
You can see that it takes a while before the swell "grabs" the hull and makes it roll in sync with the waves - rather badly, considering that the swell was about the same which you mentioned, i.e. just one foot or so. But the boat was drifting, hence with the sea exactly on her beam.
The fins are turned back on at 18" in the video, but it takes about another 10 seconds or so before they are fully effective.
Bottom line, try to focus on the boat behavior from 10" to 18", and compare it with the behavior from 28" to the end:
THAT is the difference fin stabs can make, and imho it's appropriate to call it impressive.

Btw, the Canados 70s is actually a boat as large as the Sportyacht 74, and significantly heavier.
Besides, the one in that video is equipped with 0.6 sqm fins, i.e. MUCH smaller than 1sqm!
All that said, before PF mention it, it's true that different hulls/boats require different tuning, and the same fin stabs can be a bit more or less effective on different boats, even if similar.
But the stress is on a bit more or less... :)

Then again, as I understood from your previous comments, you are also speccing the bigger engines, which according to S/skr should be able to push the boat at 38kts.
So, I assume that you are not choosing such boat with the aim of cruising at D speed and/or very low P speed in rough seas for several hours... Which is the situation where fins are vastly superior to gyros.
And if my interpretation is correct, then the idea of 2xSk9 has some merits, in principle.
To start with, no chance to hit some floating junk with exposed shafts on the external sides of the hull - and at 30+ kts, it doesn't take a whole container to make serious damages...
Besides, they would probably be great at rest, and very decent under way.
With the possibility to turn on just one at a time, whenever conditions don't require both.
And with the luxury of a partial redundancy on top.
I'm just not sure I would want to be the guinea pig of an installation never tested before... :rolleyes:
But that depends also on how confident you are on S/skr folks, I reckon.
 
Last edited:
Just a couple of thoughts on this...
I have a 2015 Fairline Sq 65 with Sleipner curved fins, not sure what size tbh, but OEM spec. We're currently based in Amalfi where, last week we were anchored off Portofino with all of its large, fast passing ferries. My boat is pretty top heavy and therefore prone to rocking and rolling and was doing so wildly until we turned on the stabs..., at which point the rolling stopped almost immediately. Except... on the few occasions when there was a big sideways wave in which case there was some slight roll because the fins' stroke had passed their maximum. Doesn't happen often at all. What you DO get is a bit of a judder as the fins are pushing and shoving against the water underneath the boat - perhaps this is the 'unnatural' motion to which you are referring. The other point is that it's taken me quite a while to get the fins 'at anchor' set up correctly and I just wonder whether the Sunseeker you trialled had been through the fine tuning? At a very basic level is on the top screen a very +/- slider via which you can increase or decrease the effect / power of the stabs - I wonder whether this was inadvertently on minimum?
Either way I'd agree with JFM's overall summary that fins are 80/90% as effective as gyro at anchor but gyro is around 30% as effective as fins underway. So for me, as someone who wants to cruise fairly long distances in sometimes quite rolly conditions, fins are by far the best option!
 
MedMilo said:
Just a couple of thoughts on this...
I have a 2015 Fairline Sq 65 with Sleipner curved fins, not sure what size tbh, but OEM spec. We're currently based in Amalfi where, last week we were anchored off Portofino ...
Click to expand...

@Porto post 48---> #losingthewilltolive

@Miles above - yup to all that, except remind me to buy you a map :D:D:D. (I presume you meant Capri). Your vector fins are 0.6m sq btw.

At anchor, both fins and gyros run out of stroke and therefore ability to stabilise, in big waves, exactly as you describe. The fins can only turn until they hit the stops, and the gyro likewise can only precess till it hits its stops. The gyro is faster out of the blocks because it doesn't need a computer to tell it to precess; the laws of physics do that, hence the AOTBE slight advantage of gyros. None of this "running out" applies to fins underway because they are a bottomless pit of antiroll torque, but it continues to apply to gyros underway just as at anchor, hence the "30%" point .
 
Last edited:
MedMilo said:
Positano!!! :rolleyes:
Click to expand...
LOL, that's what I thought while reading your previous post.
Breathtakingly beautiful village btw, by far my favorite spot of the whole "Costiera".
I never had the opportunity to see it from the sea actually, but it's bound to be a stunning anchorage background! :encouragement:
 
MapisM said:
LOL, that's what I thought while reading your previous post.
Breathtakingly beautiful village btw, by far my favorite spot of the whole "Costiera".
I never had the opportunity to see it from the sea actually, but it's bound to be a stunning anchorage background! :encouragement:
Click to expand...

Amalfi, the village next door is favourite, because it has a nice port, (and a nice bloke "Aniello " who runs that port)

being anchored in front of Positano (or even worse Capri !) is the best test for any stabilising system,
the number of heavy Itralian sport boats at semi displacement speed, and all the heavy taxi and tourists boats is countless and frustrating ...
 
I normally steer well clear of these discussions but (unusually :)) I do think Porto may be onto something. This is due to a conversation I had with Martyn (Hicks?) who used to do all of Fairline's commissioning tests. His view, even with all Fairline Olesinski hulls, was that fins / gyros worked better for one modal than another and that for some Fairline's he would recommend stabs and another gyros and others vice versa. Stabs obviously work very well for Sq74/8.

I don't think he could explain this but there must be some peculiarities in the hull or boat design that is causing this phenomenon.

So maybe the S/S that the O/P tried just doesn't work well with fins.

Of curse, if the O/P can afford fins and gyros and S/S can squeeze them in then he's got the best of both worlds (even if they would have to be used independently).
 
Last edited:
Hi Portofino,

I share with you the mantra "open boat with a dee-vee" like Itama's and I'd love to have such machine as an additional toy but one BOAT is already enough ;-)

I never met you in person, but I am sure that you are really a nice guy.

But (and please do not take it amiss), I have difficulties to read your posts. Where do sentences start and end? Syntax? etc. makes it a difficult read (true, English is not my mother tongue). Finally, the reasoning. It goes in all directions and sometimes I just don't grasp the logic.

I didn't want to offend, but I thought it could help people like me to understand you better...

Kind regards,
V



P.S. Happy to share a beer next time you are in my neighborhood in Switzerland :-)
 
Poor installation and choice of position of the fins could explain this but the physics should work for any boat if the right fins are put in the right position on the hull.

I suspect that it is not always possible to put the fins in the optimally effective position on a hull that hasn't been designed from the ground up to be fitted with stabs as stringers and bulkheads may be in the way and that is what your Martyn Hicks means.

That is one advantage with a gyro, there is more tolerance on the positioning vs effectiveness compared with fin stabs.
 
hi Guys,

As told in previous post, I have asked to the sunseeker factory to install the fins + 1 seakeeper gyro in my ordered sportyacht 74. I have got not a definitive answer but they already told me that in the engine room they dont found the place for installing an SK9 model, probably they gone propose a mitshibitsu gyro. does anyone know if this system has the same performance as a gyro from seakeeper ?
 
"Bottom line is that the best spec imo is fin+gyro together and that will be my next boat. Ideally with integrated software, but no-one is selling that yet."

I don't think you will need to wait long, Vas will soon have mastered his stabs project with an Arduino board, one or two extra jubilee clips, some duck tape, and a lot of swearing. Should be dead easy to plug that into a gyroscope:-)
 
You must log in or register to reply here.

Share this page

Top